Creatine serves as a crucial energy source in the brain, and it is delivered to brain tissue by a specialized transport protein. Approximately 42,000 males in the U.S. are affected by creatine transporter defect (CTD), in which creatine cannot enter the brain, resulting in profound learning disabilities, autistic behavior, recurring epileptic seizures and lifelong care needs. There are no U.S. Food and Drug Administration (FDA)-approved therapies for this group of patients. The lead collaborator has identified a creatine analog (CincY) that is able to penetrate the brain and serve the same role as creatine, even when creatine transporters are defective. The goal of this project is to develop CincY into an oral therapeutic to treat CTD. Summary of activities: It is estimated that creatine transporter defect (CTD) causes between 1 and 5 percent of all X-linked mental retardation. The primary clinical manifestations of the affected males are mental retardation, severe expressive language disorder and a seizure disorder, requiring dependent care for life. Creatine transporter knockout mice were treated with CincY, a repurposed small molecule that was shown to be capable of (1) getting across the blood brain barrier and (2) improving brain metabolism and cognitive function of the mice. CincY, which has an inactive Investigational New Drug (IND) Application filed for another indication, was shown to be effective in treating and reversing CTD in the knockout mouse model. Two parallel groups of patients with brain creatine deficiency syndromes (GAMT and AGAT), which have similar clinical manifestations as CTD, show significant clinical improvement when supplemented with creatine monohydrate. Creatine monohydrate supplementation is not effective in CTD because the creatine transporter gene is defective, preventing creatine from crossing the blood-brain barrier. As a result, no clinical improvement is seen in CTD patients when supplemented with creatine monohydrate. CincY has been shown to cross the blood-brain barrier, interact with creatine kinase in the brain, become phosphorylated and act in the same way as creatine as an energy buffer. The focus of this TRND collaboration is the manufacture of necessary active pharmaceutical ingredient (API); completion of a new Chemistry, Manufacturing and Control (CMC) section; and completion of all pre-clinical and IND-enabling studies. Upon completion, Lumos Pharma intends to file a new IND and begin clinical trials to study the use of CincY to treat CTD in human subjects. After TRNDs acceptance of the project, Lumos was able to secure additional funding from the Wellcome Trust to speed the teams collaborative work. TRND scientists performed pharmacokinetic studies in animal models of the disease to better understand brain uptake of CincY. Toxicology studies, formulation development, and chemistry and manufacturing are ongoing. These studies will enable an IND application to be filed with the FDA. To support future clinical trials of CincY, TRND is developing a prospective natural history study of the disease course in patients.